Proceedings of IOE Graduate Conference, 2016 pp. 139–146
Dynamic Characteristics Study of RCC Building using Micro Tremor measurement in Thapathali, Kathmandu Nepal
Thaman Bahadur Khadka 1*, Rishi Ram Parajuli 2, Hari Ram Parajuli 3
1 Department of Civil Engineering, Thapathali Campus, Institute of Engineering, Tribhuvan University, Nepal 2 Department of Urban Management, Kyoto University 3 Department of Civil Engineering, Thapathali Campus ,Institute of Engineering, Tribhuvan University, Nepal *Corresponding Email: [email protected]
Abstract At April 25 2015, Nepal face big Earthquake of magnitude Mw 7.8 having epicenter at Gorkha District at approximate 77 km Northwest of Kathmandu. This results in huge loss of life and properties, more than 10,000 people losses their life. Earthquake itself does not harm us but man-made structure, create problem during the Earthquake. Low grade construction material and haphazard construction of the structures are the main element, which are responsible for damage of structure. As a mitigation measures, appropriate technique and methodology should be implemented during the construction process. Micro tremor measurement of E- building of Thapathali campus were analyzed to determine the natural frequency of the model building. Natural frequency of the building is determined from the Fourier spectra and its estimated value is 2.48 Hz and 2.37 Hz in longitudinal and transverse direction respectively. Similarly rocking frequency and translational frequency of the building is also determined from the spectral ratio of the various location. Keywords Micro tremor measurement – RCC Building – Natural frequency – fourier spectra
Introduction The Gorkh Earthquake (Mw7.8) had occurred at 11:56 NST on 25 April 2015 with an epicenter 77 km (48 Nepal rests on a major fault-line between two tectonic miles) northwest of Kathmandu, the capital city of plates. One bears India, pushes north and east at a rate Nepal, that is home to nearly 1.5 million inhabitants, of about 2cm (0.8 inches) per year against the other, and at a focal depth of approximately 10-15 km This which carries Europe and Asia. This process created the earthquake was the one of the most powerful Himalaya mountain range and causes earthquakes when earthquakes to strike Nepal since the 1934 Nepal-Bihar strain built up along the fault gives way periodically, earthquake (Mw8.1). Based on the information by the thrusting the overlying landmass up and outward. United Nations, eight million people have been affected Himalayan Frontal Thrust (HFT), the Main Boundary by the Gorkha earthquake in Nepal, more than a quarter Thrust (MBT) and Main Central Thrust (MCT) are the of the Nepal’s population. Gorkha earthquake was of main faults in the region and they are part of the Great low frequency dominant in Kathmandu valley that saved Himalayan range. Presently the main tectonic much of structures having high natural frequency. If the displacement zone is the Himalayan Frontal Thrust ground motion was of high frequency dominant, Fault (HFTF) System, which comprises Himalayan damages would be much worse than that happened [2]. Frontal Fault at the edge of the Indo-Gangetic plains, The main cause of loss of life and property is weak and and several active anticlines and synclines to the north. haphazard construction of Masonry Building, RCC The Himalayan front in the western Nepal is Building, Bridges, Dams, and Towers etc. Raising the characterized by several discontinuous segments of the need of reduction in earthquake disaster, investigation HFT and its subsidiary faults [1]. regarding the capacity of the building and the ground Dynamic Characteristics Study of RCC Building using Micro Tremor measurement in Thapathali, Kathmandu Nepal
property must be identified before the construction function of the surface. It has now been established that procedure. As the part of the project micro tremor the horizontal micro tremor spectra often show the measurement was made in the E- Building of characteristics of the source rather than the transfer IOE-Thapathali Campus Kathmandu. The property of function of a site. micro tremor was used to analyze Natural frequency, Yukta Nakamura in 1989, modified micro tremor Rocking frequency and Translation frequency of the analysis by proposing a new technique, generally respective Building. referred to as the H/V method. In this technique, it was shown that the source effect can be minimized by normalizing the horizontal spectral amplitude with the vertical spectral amplitude. Assuming that the shear wave dominates the micro tremor, Nakamura indicated that the horizontal-to-vertical (H/V) spectral ratio of micro tremors at a site roughly equals the S-wave transfer function between the ground surface and bedrock at a site. This means that the H/V peak period and peak value itself correspond to the natural site period and amplification factor respectively (NAKAMURA, 1989). Figure 1: Distribution of the active faults in and around Due to the close relation between the nature of micro Nepal Himalaya (from Nakata and Kumahara 2002 tremors and the fundamental dynamic behavior of the surface soil layer, these small vibrations are well-known and useful in the field of earthquake engineering. The Micro-tremor is a low amplitude (in the order of technique of micro tremors measurement and analysis micrometres) ambient vibration of the ground caused by has been successful for micro zoning in many places man-made or atmospheric disturbances. The term around the world. This technique has the advantage Ambient Vibrations is now preferred to talk about this of being a fast and easy way to estimate the effect of phenomenon. Observation of micro tremors can give ground motion characteristics due to an earthquake. The useful information on dynamic properties of the site characteristics of micro tremors are dependent on the such as predominant period and amplitude. type of deposits. At the same time, the amplitude is Microtremor observations are easy to perform, not stable. Site effect plays an important role in micro inexpensive and can be applied to places with low tremors measurements [4]. seismicity as well, hence, micro tremor measurements can be used conveniently for seismic micro zonation. Stable estimation of the predominant frequency and the 2. Methodology amplification factor can be made even in presence of a certain degree of the artificial tremor and there is no The Building under study was approximately 15 years need any more for time restriction on the micro tremor old and four story with its basement located in measurement [3]. Thapathali, Kathmandu the capital city of Nepal. RCC framed with infill brick masonry building having L shape and approximate height above the plinth level was 1. Background 40 feet. The building was highly suffered from the Gorkha Earthquake-2015 and some part of the building After the pioneering work by Kannai and Tanaka, many got damaged which are under maintenance. The plan of researchers have investigated the applicability and building is shown as below. reliability of the micro tremor method. The major drawback of the method proposed by Kannai and Dynamic characteristic study of the E-Building of Tanaka was that they considered the Fourier spectra of Thapathali campus using Micro-tremor data observed horizontal motions to reflect the transfer Micro-tremor data was taken with the application of the
140 Proceedings of IOE Graduate Conference, 2016
Seismometer at different part of the building and these different modes [5]. data were analyzed for the determination of the Natural Determination of the Rocking frequency Frequency, Rocking Frequency and Translation Frequency of the Building . The ratio of the Fourier Spectrum between the other floor (Ground floor, 1st, 2nd, 3rd and 4th) with the Basement was plotted in the frequency domain for both longitudinal and transverse direction .The frequency corresponding to the respective highest Fourier ratio is termed as the natural rocking frequency of the building at various modes. Determination of the Translation frequency The ratio of the Fourier Spectrum between the same floor micro tremor data was plotted in the frequency domain for both longitudinal and transverse direction .The frequency corresponding to the respective highest Fourier ratio is termed as the Translation frequency of the building at various modes.
3. Results
Three orthogonal component of the micro tremor measurement is plotted as shown in the figure below.
7 x 10 Longitudinal Component Figure 2: plan of the building showing the location of 1 micro tremor measurement (1 to 8 0
Acceleration 7 x 10 Transverse Component Determination of Natural Frequency of the Building −11 Duration (sec) Micro tremor measurement in the E-Building at various location is shown in the plan above. The Micro-tremor 0
Acceleration 7 data was obtained in three orthogonal directions along x 10 Vertical Component −11 with time. Assuming that all the records were stationary Duration (sec)
, then overall data are cut into six segments having no of 0 data in each segment is in the form of 2 power n which Acceleration is essential for the Fast Fourier Transformation (FFT). −1 The recorded data were used to determine the Natural Duration (sec) Frequency of the Building. The ambient vibration of the Figure 3: Sample micro tremor Record building get amplified at its natural Frequency of the structure which can be identified from the Fourier spectrum and this process is said to be Structural Natural Period of the Building. Identification Technique [5]. The microtremor data at various location of the building Fourier Spectra of all the records together with was used to construct the fourior spectra and the longitudinal and transverse direction at different part of frequency at the highest amplitude is taken as the the building were calculated and plotted in the graph. natural Frequency of the building. The avg frequency of Frequency corresponding to the highest amplitude are the building is seems to be 2.48 Hz in longitudinal said to be the Natural Frequency of the building at direction and 2.37 Hz in transverse direction.
141 Dynamic Characteristics Study of RCC Building using Micro Tremor measurement in Thapathali, Kathmandu Nepal
5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 4: Fourier spectra of Basement 7, 8, and 1 Figure 8: Fourier Spectra, GF, 3, 4, and, 5
5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 5: Fourier Spectra, Basement 2 and GF 1 and 2 Figure 9: Fourier Spectra GF 1and 1st Floor 7and 8
5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 2
1.5 1.5 1.5 1.5
1 1 1 1
Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 4 2 2 3 3 1.5 1.5 2 2 1 1
Amplitude 1 Amplitude 1 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 6 1.5 1.5 1.5 4 1 1 1
Amplitude 2 Amplitude Amplitude Amplitude 0.5 0.5 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 6: Fourier Spectra, Basement 3, 4 and 5 Figure 10: Fourier Spectra 1st Floor 1,2 and 3
5 5 5 5 x 10 x 10 x 10 x 10 4 2 2 2
3 1.5 1.5 1.5
2 1 1 1
Amplitude 1 Amplitude 0.5 Amplitude 0.5 Amplitude 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 5 2 2 2
4 1.5 1.5 1.5 3 1 1 1 2 Amplitude Amplitude 0.5 Amplitude 0.5 Amplitude 0.5 1
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 5 5 x 10 x 10 x 10 x 10 2 2 2 3
1.5 1.5 1.5 2 1 1 1
Amplitude Amplitude Amplitude Amplitude 1 0.5 0.5 0.5
0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 7: Fourier spectra Basement 6 and GF 1 and 2 Figure 11: Fourier spectra 1st floor 4,5 and 6
142 Proceedings of IOE Graduate Conference, 2016
5 5 x 10 x 10 2 3
1.5 Table 1: Natural Frequency determination 2 1
Amplitude Amplitude 1 0.5 Fig No Floor Location X (Hz) Y(Hz) 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 x 10 x 10 3 2 4 Basement 7 3.17 2.30
1.5 2 4 Basement 8 2.44 2.34 1
Amplitude 1 Amplitude 0.5 4 Basement 1 2.10 2.20 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 x 10 x 10 5 Basement 2 4.00 3.91 2 2 1.5 1.5 5 G Floor 1 3.96 2.83 1 1 Amplitude 0.5 Amplitude 0.5 5 G Floor 2 3.22 2.27 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 6 Basement 3 3.17 3.17 Figure 12: Fourier Spectra 2nd floor 7,8 and 1 6 Basement 4 3.08 1.66 6 Basement 5 3.52 3.61
5 5 x 10 x 10 7 Basement 6 2.54 3.13 2 2 1.5 1.5 7 G Floor 7 1.86 2.05 1 1 Amplitude 0.5 Amplitude 0.5 7 G Floor 8 3.91 3.08 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 x 10 x 10 8 G Floor 3 3.76 3.32 3 3
2 2 8 G Floor 4 2.30 2.15
Amplitude 1 Amplitude 1 8 G Floor 5 4.54 2.73 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 9 G Floor 6 1.90 1.90 x 10 x 10 3 3
2 2 9 1st floor 7 2.34 2.30
Amplitude 1 Amplitude 1 9 1st floor 8 2.30 2.00 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 10 1st floor 1 1.95 2.10 Figure 13: Fourier Spectra 2nd floor 2,3 and 4 10 1st floor 2 1.90 2.10 10 1st floor 3 1.95 2.05
5 5 11 1st floor 4 2.30 2.20 x 10 x 10 3 3
2 2 11 1st floor 5 2.30 2.20
Amplitude 1 Amplitude 1 11 1st floor 6 1.86 2.25 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 12 2nd Floor 7 2.25 2.25 x 10 x 10 3 3
2 2 12 2nd Floor 8 2.25 2.25
Amplitude 1 Amplitude 1 12 2nd Floor 1 2.25 2.05 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 13 2nd Floor 2 1.90 2.20 x 10 x 10 3 3 13 2nd Floor 3 1.95 2.88 2 2
Amplitude 1 Amplitude 1 13 2nd Floor 4 1.95 2.10
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 14 2nd Floor 5 1.95 2.05 Figure 14: Fourier Spectra 2nd floor 5 and 6, 3rd floor 14 2nd Floor 6 1.90 2.25 7 14 3rd Floor 7 2.30 2.15 15 3rd Floor 8 2.30 2.20 15 3rd Floor 1 2.30 2.25 5 5 x 10 x 10 3 4 15 3rd Floor 2 1.90 1.95 3 2
2
Amplitude Amplitude 1 1 16 3rd Floor 3 1.90 2.10
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 16 3rd Floor 4 1.90 2.20 5 5 x 10 x 10 2 3
1.5 16 3rd Floor 5 1.90 1.95 2 1
Amplitude Amplitude 1 0.5 17 3rd Floor 6 1.86 2.30
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Avg - - 2.48 2.37 5 5 x 10 x 10 4 5
4 3 3 2 2 Amplitude 1 Amplitude 1
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 15: Fourier spectra, 3rd floor 8, 1 and 2
143 Dynamic Characteristics Study of RCC Building using Micro Tremor measurement in Thapathali, Kathmandu Nepal
5 5 x 10 x 10 4 4 10 10 3 3
2 2
Amplitude 1 Amplitude 1 5 5
0 0 F3/FB F3/FB 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 x 10 x 10 3 2 0 0 0 5 10 0 5 10 1.5 2 1 Frequency (Hz.) − along X Frequency (Hz.) − along Y
Amplitude 1 Amplitude 0.5 Figure 19: Spectral ratio between 3rd Floor with
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Basement at 1st location 5 5 x 10 x 10 2 2
1.5 1.5
1 1
Amplitude 0.5 Amplitude 0.5
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 10 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 8 8
6 6
Figure 16: Fourier Spectra, 3rd floor 3, 4 and 5 F0/FB 4 F0/FB 4 2 2
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y
10 10
8 8
6 6
F1/FB 4 F1/FB 4
2 2
0 0 5 5 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 x 10 x 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 2 2 10 10 8 8
6 6
F2/FB 4 F2/FB 4
1 1 2 2
0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Amplitude 0 Amplitude 0 0 5 10 0 5 10 Figure 20: Spectral ratio between ground floor, 1st and Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 17: Fourier Spectra 3rd Floor 6 2nd Floor with Basement at 2nd location
Rocking Frequency of the Building 20 20
Rocking frequency of the building was obtained by 10 10 taking the Fourier Spectral ratio between Ground F3/FB F3/FB 0 0 Floor,1st Floor,2nd floors and 3rd floor with Basement 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y as shown in the figure below. From the observation first Figure 21: Spectral ratio between 3rd Floor with mode rocking frequency is 1.898 Hz in Longitudinal Basement at 2nd location and 1.935 in Transverse Direction respectively.
10 10 10 10 5 5
F0/FB F0/FB 5 5 0 0 F0/FB F0/FB 0 5 10 0 5 10 0 0 Frequency (Hz.) − along X Frequency (Hz.) − along Y 0 5 10 0 5 10 10 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 10 10 5 5
F1/FB F1/FB 5 5 F1/FB F1/FB 0 0 0 5 10 0 5 10 0 0 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y 10 10 10 10
5 5 5 5 F2/FB F2/FB F2/FB F2/FB
0 0 0 0 0 5 10 0 5 10 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 18: Spectral ratio between ground floor, 1st and Figure 22: Spectral ratio between ground floor, 1st and 2nd Floor with Basement at 1st location 2nd Floor with Basement at 3rd location
144 Proceedings of IOE Graduate Conference, 2016
10 20 Translation Frequency of the Building
5 10
F3/FB F3/FB Translation Frequency of Building was obtained from
0 0 the Spectral ratio between various locations of same 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y floors as shown in the figure given below. From the Figure 23: Spectral ratio between 3rd Floor with observation the translation frequency of the building is Basement at 3rd location 2.555 Hz and 2.930 Hz in Longitudinal and Transverse direction respectively.
10 10
5 5 F0/FB F0/FB
0 0 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 4 4 10 10 3 3
F2/F1 2 F2/F1 2
1 1
0 0 5 5 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y
F1/FB F1/FB 5 5
4 4 0 0 3 3
0 5 10 0 5 10 F3/F1 2 F3/F1 2 1 1
Frequency (Hz.) − along X Frequency (Hz.) − along Y 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 20 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 10
4 8
3 6
10 5 F4/F1 2 F4/F1 4 1 2 F2/FB F2/FB 0 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0 0 Frequency (Hz.) − along X Frequency (Hz.) − along Y 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 26: Spectral ratio between different positions of Figure 24: Spectral ratio between ground floor, 1st and Basement 2nd Floor with Basement at 4th location
15 10
10 5
F3/FB 5 F3/FB
0 0 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 25: Spectral ratio between 3rd Floor with Basement at 4th location
5 5
Table 2: Roking Frequency determination F2/F1 F2/F1 Fig No Floor location x y 0 0 0 5 10 0 5 10 18 F0/FB 1 1.855 1.904 Frequency (Hz.) − along X Frequency (Hz.) − along Y 18 F1/FB 1 1.953 1.904 5 5 18 F2/FB 1 2.295 1.904 19 F3/FB 1 2.344 2.295
20 F0/FB 2 1.807 2.002 F3/F1 F3/F1 20 F1/FB 2 1.855 2.051 0 0 0 5 10 0 5 10 20 F2/FB 2 1.855 2.100 Frequency (Hz.) − along X Frequency (Hz.) − along Y 21 F3/FB 2 1.904 1.953 5 5 22 F0/FB 3 2.930 2.051 22 F1/FB 3 1.904 0.342
22 F2/FB 3 1.953 2.197 F4/F1 F4/F1 23 F3/FB 3 1.904 2.100 0 0 24 F0/FB 4 0.293 2.100 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 24 F1/FB 4 1.904 1.953 24 F2/FB 4 1.807 2.002 Figure 27: 25 F3/FB 4 1.807 2.100 Spectral ratio between different positions of Average - - 1.898 1.935 GF
145 Dynamic Characteristics Study of RCC Building using Micro Tremor measurement in Thapathali, Kathmandu Nepal
5 5 Table 3: Translation Frequency determination
Fig No Floor location x y F2/F1 F2/F1 26 BM 2nd/ 1st 4.102 3.711 0 0 0 5 10 0 5 10 26 BM 3nd/ 1st 4.053 3.564 Frequency (Hz.) − along X Frequency (Hz.) − along Y 26 BM 4nd/ 1st 3.272 3.223 5 5 27 GF 2nd/ 1st 4.199 3.906 27 GF 3nd/ 1st 4.248 3.906 27 GF 4nd/ 1st 4.297 0.781 F3/F1 F3/F1 28 1st 2nd/ 1st 0.830 3.711 0 0 0 5 10 0 5 10 28 1st 3nd/ 1st 0.732 4.004 Frequency (Hz.) − along X Frequency (Hz.) − along Y 28 1st 4nd/ 1st 2.49 4.981 5 5 29 2nd 2nd/ 1st 1.758 2.539 29 2nd 3nd/ 1st 1.758 3.076
F4/F1 F4/F1 29 2nd 4nd/ 1st 1.758 2.148 0 0 30 3rd 2nd/ 1st 1.904 1.907 0 5 10 0 5 10 30 3rd 3nd/ 1st 1.904 1.758 Frequency (Hz.) − along X Frequency (Hz.) − along Y 30 3rd 4nd/ 1st 1.025 0.732 Figure 28: Spectral ratio between different positions of Average - - 2.555 2.930 1st Floor 4. Conclusion
5 5 Dynamics Characteristics of E-Building Thapathali Campus was analyzed by using Micro tremor reading. F2/F1 F2/F1 Natural Frequency of the E-Building was obtained from 0 0 0 5 10 0 5 10 the Fourier Spectrum and its value is 2.48 Hz in Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 longitudinal and 2.37 Hz in Transverse direction. Rocking frequency was obtained from spectral ratio
F3/F1 F3/F1 between different floors and its value is 1.898 Hz and 0 0 0 5 10 0 5 10 1.935 Hz in X and Y direction respectively. Similarly Frequency (Hz.) − along X Frequency (Hz.) − along Y 5 5 Translation frequency was obtained from the spectral ratio between various location of the same floor and its
F4/F1 F4/F1 value was determined as 2.555 Hz and 2.930 Hz in X 0 0 0 5 10 0 5 10 and Y direction respectively. Frequency (Hz.) − along X Frequency (Hz.) − along Y Figure 29: Spectral ratio between different positions of 2nd Floor References [1] Omer AYDAN and R.U. The quick report on the 2015 gorkha (nepal) earthquake and its geo-engineering 5 5 aspects. 2015. [2] R.R Parajuli and J. Kiyono. Ground motion F2/F1 F2/F1 characteristics of the 2015 gorkha earthquake, survey 0 0 0 5 10 0 5 10 of damage to stone masonry structures and structural Frequency (Hz.) − along X Frequency (Hz.) − along Y field tests. frontiers in built environment. 2015. 5 5 [3] Yataka Nakamura. A method of dynamics characteristics
F3/F1 F3/F1 estimation of the sub surface using the microtremor on
0 0 the ground surface. Railway Technical research Institute, 0 5 10 0 5 10 Frequency (Hz.) − along X Frequency (Hz.) − along Y 30 No 1, 1989. 5 10 [4] M. M. DYKMEN. Application of microtremors to
5 seismic microzoning procedure. 2003. F4/F1 F4/F1 [5] Hari Ram Parajuli, Junji Kiyono, Masatoshi Tatsumi, 0 0 0 5 10 0 5 10 Yoshiyuki Suzuki, Hisashi Umemura, Hitoshi Taniguchi, Frequency (Hz.) − along X Frequency (Hz.) − along Y Kenzo Toki, Aiko Furukawa, and Prem Nath Maskey. Figure 30: Spectral ratio between different positions of Dynamic characteristic investigation of a historical masonry building and surrounding ground in kathmandu. 3rd Floor Vol.6 No.1, 2011.
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